1. Field of the Invention
The present invention relates to the field of panoramic still and motion photography.
2. Related Art
Imaging systems exist that include more than one camera in a rosette formation attached to a vehicle. Those imaging systems may be used to capture panoramic images, for example, along a street. Each camera includes an entrance pupil. Having multiple entrance pupils at different locations can cause spatial parallax. Parallax refers to a perceived shift of an imaged object against a background caused by the different viewpoints of the entrance pupils of the cameras. Parallax is a particular problem when stitching together images from multiple cameras, since it can cause ghosting of foreground objects when background objects are aligned in the region where adjacent images overlap.
Mirrors have been used to avoid parallax in panoramic imaging. For example, Disney's Circle-Vision 360° system uses mirrors to view the world through multiple co-located entrance pupils. This can result in zero parallax. However, making and using the necessary large mirrors is difficult. Also, this technique limits the vertical field of view.
Each camera in the rosette formation includes an image sensor that converts an optical signal into an electrical signal to form an image. Two types of image sensors avoid the need for a mechanical shutter—an interline-shutter charge-coupled device (CCD) or a complementary metal oxide semiconductor (CMOS) sensor.
The CMOS sensor typically has a rolling shutter, which exposes different lines of the scene at slightly different times, in a sequence that rolls across the image. The rolling shutter can lead to image distortion, such as warping, when the camera is moving relative to the scene or subject. Some work has been done to compensate for the image distortion. Wilburn et al. describes using a rolling shutter timing offset to process and correct distortions induced by motion of a subject of an image. See Wilburn et al., “High-Speed Videography Using a Dense Camera Array”, 2004 IEEE Computer Society Conference on Computer Vision and Pattern Recognition (CVPR'04), Vol. 2, pp. 294-301.
The interline-shutter CCD avoids the image distortion issues of the rolling shutter CMOS sensor. However, the interline-shutter CCD can suffer from blooming and streaking. Blooming and streaking occur when a portion of the sensor is over-exposed, causing light to spillover to adjacent pixels or into the readout CCD structure.
What is needed is an imaging apparatus that reduces distortion and spatial parallax, while avoiding the blooming and streaking issues associated with CCDs.